1. Field of the Invention
The present invention relates to a testing apparatus for a steering apparatus which includes a controller for controlling a steering actuator according to a steering detection output of a torque sensor.
2. Description of Related Art
Conventionally, a motor vehicle is mounted with an electric power steering apparatus which performs a steering assist operation by applying a steering assist force to a steering mechanism according to a steering torque applied to a steering wheel. More specifically, the electric power steering apparatus includes a torque sensor which detects the steering torque applied to the steering wheel, an electric motor which applies the steering assist force to the steering mechanism, and an in-vehicle controller (ECU: electronic control unit) which controls the driving of the electric motor according to the steering torque.
A control parameter (control constant) to be employed by the in-vehicle controller for controlling the electric motor is preliminarily set for each type of motor vehicles. That is, the control parameter is set such that a steering characteristic of a standard motor vehicle of a specific vehicle type is equal to an ideal or nominal steering characteristic (target characteristic).
However, mass-produced complete motor vehicles do not have exactly the same characteristics as the standard motor vehicle, but suffer from cumulative variations in mechanical characteristics of individual components. Such mechanical variations vary from one motor vehicle to another. Therefore, the steering characteristic of the motor vehicle mounted with the electric power steering apparatus is not necessarily equal to the target characteristic, making it difficult to provide an ideal steering feeling.
A testing apparatus for a steering apparatus disclosed in Japanese Unexamined Patent Publication No. 2003-261046 is configured to detect abnormality of a steering apparatus by monitoring an output to a steering motor while applying a rotation torque to an input shaft of the steering apparatus, and comparing the output with a reference value. Even with the use of this testing apparatus, it is impossible to adjust the control parameter according to the mechanical variations among different motor vehicles, making it difficult to provide a desired steering characteristic.